Page 53 - Mouse Molecular Genetics

Full Abstracts
Program number is above title. Author in bold is the presenter.
53
Imaging
53
Optical Imaging of the Embryonic Mammalian Cardiovascular System. Mary E. Dickinson
.
Molecular Physiology &
Biophysics, Baylor College of Medicine, Houston, TX.
The cardiovascular system is the first functional organ system to develop in mammals. Not long after the heart begins to beat,
the cardiovascular system becomes essential for the normal development of the embryo and vitality. Interestingly, the heart,
vessels and early hematopoietic cells are all needed for continued normal development and defects in any of these three cell types
can lead to lethality as well as an array of secondary defects that may mask which cell type is primarily affected. In the past few
years, we have developed live imaging strategies using confocal and multi-photon microscopy as well as Optical Coherence
Tomography (OCT). These studies have provided new insights into early cardiovascular development and OCT is emerging as a
robust tool for evaluating early lethal mutations in large-scale gene knock-out screens. These results will be discussed.
54
Imaging techniques in
Drosophila
to delineate candidate roles of calcium in murine lung and neural
development. Danielle V. Bower
1
,
Scott E. Fraser
1
,
Edwin C. Jesudason
2
. 1)
Biology and the Biological Imaging Center,
California Institute of Technology, Pasadena, CA; 2) Department of Surgery, Children's Hospital Los Angeles, Los Angeles, CA.
The
Drosophila
tracheal system and mammalian lungs form in a stereotyped manner via defined patterns of cell migrations and
branching. However, what regulates the branching patterns and timing of branch formation is incompletely understood. We
investigated the role of calcium signaling in tracheal branching in
Drosophila
embryos by permeablizing the embryos and
applying small molecule inhibitors to perturb calcium dynamics. Disrupting calcium dynamics affects the patterning of
the
Drosophila
tracheal system as well as neural tracks in the central nervous system. We are now extending these techniques to
the mammalian lung to study the role of calcium signaling in the regulation of branching.
55
Live imaging the pluripotent state
in vitro
and
in vivo
.
Panagiotis Xenopoulos
1*
,
Minjung Kang
1,2
,
Anna-Katerina
Hadjantonakis
1
. 1)
Developmental Biology Program, Sloan-Kettering Institute, New York, NY; 2) Biochemistry, Cell and
Molecular Biology Program, Weill Graduate School of Medical Sciences of Cornell University, New York, NY.
Pluripotent stem cell-based therapies hold enormous promise for patients with degenerative and other diseases. However, a
deeper understanding of the mechanisms driving pluripotent cells to self-renew or differentiate into specific lineages
in
vitro
and
in vivo
is needed in order to use these cells for clinical applications in a safe and effective manner. To that end, it was
recently demonstrated that pluripotent stem cell populations of the same genetic background exhibit heterogeneous expression of
pluripotency-associated genes. Remarkably, these heterogeneities have been shown to correlate with dynamic fluctuations in the
expression of certain pluripotency-associated factors, suggesting the existence of inter-convertible substates within pluripotent
stem cell compartments. It is believed that such heterogeneity and fluctuating substates may represent a hallmark of all
pluripotent cell types, reflecting a propensity for the decision to self-renew or differentiate. Interestingly, these heterogeneities
have not been observed yet in the early mammalian embryo, from where pluripotent cells are derived. An essential tool for
investigating the relationship between heterogeneous gene expression and cell fate decisions is live cell imaging. By using BAC
recombineering, we have developed a series of novel, universal, high-resolution live imaging reporters of the pluripotent state.
We show that these pluripotency-associated imaging reporters are nuclear localized in cultures of mouse embryonic stem (ES)
cells and provide excellent single-cell resolution and tracking of cells over time. We are using these imaging tools in order to
probe heterogeneities and characterize fluctuating substates in cultures of pluripotent stem cells
in vitro
.
Moreover, these
reporters have allowed us to visualize the emergence of the pluripotent epiblast lineage in mouse blastocyst stage embryos, as
well as to examine whether the heterogeneities observed in culture exist
in vivo
.
These studies should help elucidate how cells
differentiate or decide to remain in a pluripotent state
in vitro
and
in vivo
.
56
Imaging of cellular dynamics underlying the immune tissue organization. Takaharu Okada
1,2
. 1)
Research Unit for
Immunodynamics, RCAI, RIKEN, Yokohama, Kanagawa, Japan; 2) PRESTO, Japan Science and Technology Agency, Tokyo,
Japan.
The immune tissues such as lymph nodes are structurally compartmentalized so that relevant cell types for each mode of
immune responses are co-localized and able to access each other. During the last decade, live tissue imaging, in particular using
two-photon laser microscopy, has advanced our understanding of immune cell trafficking mechanisms. Studies using this
technique have contributed to reveal molecular requirements for leukocyte migration and interaction in native tissue
environments. In this talk, I will present data from live imaging experiments to show dynamics of B cells, T cells, and dendritic
cells during adaptive immune responses. It will be discussed how dynamics of activated B cells, which is regulated by their
differential responsiveness to multiple trafficking cues, contributes to remodeling of B cell follicles to form germinal centers for